1. Field of the Invention
The present invention relates, in general, to vehicle headlight aiming apparatus and methods.
2. Description of the Art
Vehicle headlights project a light beam forward of a vehicle to illuminate the roadway for a driver. High beam and low beam headlights either in separate light bulbs or implemented by dual filaments and lens in a single bulb project different light patterns.
Headlights must be aimed according to standards, such as an SAE standard in the United States and different but similar standards in Europe and Japan. Typically, a light beam is projected onto a target board set 25 feet in front of the vehicle. An ideal light beam pattern or image imprinted on the target board is manually compared with the light beam image or pattern from the vehicle and manual adjustments, as necessary, made to the headlight support structure to properly coincide the headlight beam pattern with the standard image pattern.
Another method utilizes the reflection of a light beam from a vehicle headlight through a lens and off of a screen to a camera which produces a digitized image of the reflected light beam. The focal length of the lens and the distance between the lens and the screen are optically equivalent to the 25 foot distance between the headlight and target board described above. The digitized image is then analyzed by an algorithm executed by a processor to locate the highest intensity pattern or "hot spot" which is considered to be the main optical axis of the headlight. The headlight is adjusted, as necessary, to align the hot spot with the hot spot of a properly aligned headlight according to the various standards.
Different aiming algorithms are necessary since the intensity contours of different style lamps varies by the particular market. Both left hand and right hand headlight algorithms are also needed. Typically, however, these algorithms are very sensitive to hardware noise and require additional processing to remove "aim bounce" which has the effect of reporting varying aimpoint values during static repeatability testing.
Since all headlights including both low and high beam lights in each vehicle made in a manufacturing plant must be properly aimed, consideration must be taken as to the integration of the headlight aiming procedure in the typically high speed production line. Due to high production rates, vehicles have been directed to a plurality of individual headlight aiming stations. The multitude of stations adds expense to the aiming operation and may introduce variability in the aiming results between the different stations. Other aiming apparatus, which have been incorporated directly into the production line, must be moved into a position in front of each vehicle at the proper time. This has met with problems in repeatably aligning the headlight aiming apparatus with each vehicle.
Thus, it would be desirable to provide a headlight aiming apparatus and method which utilizes an improved algorithm for greater aiming accuracy. It would also be desirable to provide a headlight aiming apparatus and method which is usable with a plurality of different headlight image patterns. It would also be desirable to provide a headlight aiming apparatus which can be easily integrated into a vehicle assembly line.